Investigation of Physio-Mechanical and Micro-Structural Properties of Hybrid Geopolymer Concrete as Partial Replacement of Bagasse Ash with Cement

Abstract

The utilization of waste products made of aluminosilicate materials in the production of geopolymer concrete at heat curing is a solution that reduces the economic impact of cement production, since cement is considered one of the most expensive components of concrete production. Various researchers have investigated the applicability of Ordinary Portland Cement (OPC) in producing hybrid geopolymer concrete to overcome the problem of getting improved hardened concrete properties using pure geopolymer concrete at ambient curing temperature. However, the impact of replacing sugarcane bagasse ash (SCBA) with OPC in hybrid geopolymer concrete under immersion curing has not been studied yet. In this regard this study aims to investigate the effects of incorporating OPC as a partial substitute for SCBA in geopolymer concrete production. Factors such as workability, compressive strength, water absorption, sulfate attack, and microstructure, along with economic implications, were analyzed. In addition, the chemical composition of sugarcane bagasse ash was examined through complete silica analysis. To develop the concrete mix for C-25 concrete grade, the American Concrete Institute's mix design method was employed. The study consisted of producing two mixes: a control mix made up of cement, water, fine and coarse aggregate, and a replacement mix with varying weight percentages of OPC (5%, 10%, 15%, 20%, and 25%) substituted for sugarcane bagasse ash. The alkaline activator solution of sodium silicate and sodium hydroxide was utilized to activate the bagasse ash as a binder. Additionally, sugarcane bagasse is classified as a material with high silicon dioxide content and pozzolanic properties. As the OPC content increased in the concrete mix, the workability of the concrete decreased due to extra water demand. However, the compressive strength at 28 days of curing saw a 23.31% improvement for the 15% replacement mix compared to the control mix (100% OPC). The cause of the increase in the compressive strength of the concrete was due to the creation of semi hydrate gel and geopolymer gel. Therefore, a 15% replacement mix showed the best results in terms of compressive strength. Moreover, the pores inside the concrete matrix were filled due to CSH and geopolymer gel formation, leading to lower water absorption in the concrete with a 15% replacement mix. Furthermore, adding OPC to SCBA based geopolymer concrete was improve the sulfate attack resistance of the hybrid geopolymer concrete. The hybrid geopolymer concrete was analyzed microstructurally and compared to the control mix. The study found that the mix with a 15% replacement had calcium silicate hydrate gels and geopolymer gel. The study concluded that by utilizing OPC up to 15% as a partial replacement for sugarcane bagasse ash, the compressive strength of hybrid geopolymer concrete can be improved while also lowering the cost of cement manufacturing